Various roofing structures and systems are known. The object of most roofing systems is to provide insulation for the building which the roof covers, to keep the building dry and yet to prevent water vapor from accumulating within the roofing system or structure. Accumulation of water vapor is damaging or destructive to the roofing system. Yet it is difficult to keep water out of the building and at the same time to prevent build-up of water vapor within the roofing structure. In addition, the roofing system must be strong enough to support any wind load and snow loads to which it is subjected, to permit a person to walk on the roof, and (where desired) to support an aesthetically pleasing exterior covering which constitutes the top layer of the roofing structure. Existing roofing systems achieve the aforesaid objects with varying degrees of success. In some cases there is a tradeoff in which performance in one area is sacrificed in order to achieve top performance in another area. In particular, it is difficult to keep a building dry and at the same time to prevent the build-up of water vapor within the roofing structure. Various constructions have been proposed in order to achieve both objects.
Significant improvements in roof insulation have been accomplished with the insulated roof board structures shown in U.S. Pat. Nos. 4,804,578 and 5,069,950, both to Anthony J. Crookston, Sr. (the inventor herein). A foamed plastic insulation member as described in U.S. Pat. No. 5,069,950 is a particularly preferred insulation member for roofing systems. Structures of these patents provide excellent insulation systems for both insulating a building and for venting water vapor efficiently so that it does not condense within the roofing structure.
A pitched roof, i.e., a sloped roof with or without gutters at the caves, is subject to severe infiltration of water, condensed moisture, at the juncture of roof sheathing and fascia board. This is especially true on low-pitched roofs due to a siphoning action. Both low pitched and steep pitched roofs are subject to water infiltration and damage as are a result of overflow when an ice dam forms at the roof's eave edge. When this happens, the resulting damage to the soffit materials, rafter ends, and roof sheathing is extensive. In those instances where an overhang is not employed, severe damage is also inflicted to the interior of the structure requiring the removal of drywall or plaster, repairing any damage to windows or doors, and repainting.
Flat roofs are also subject to water infiltration and to damage, particularly along the perimeter of a roof at a juncture between the roof and a wall or parapet which extends above the outer surface of the roof.
While the state of the art is aware of a number of roofing systems, including systems which include insulation, very little tension has been paid to structures at the perimeter of a roof which address the problems noted above the entry of air into an air space beneath the roof for purposes of ventilation.